Resistor identification

Thread Starter

AlbertHall

Joined Jun 4, 2014
12,020
I have a (faulty) resistor: Black, Brown, Green, Silver, Brown - 0.15Ω?
It is about 18mm x 5mm.
It is in series with a battery being charged at 2A.
I need to replace this.
Did I get the value right?
Is it anything special?
What wattage do you think it is?

I believe it is a shunt for measuring the current to operate the circuit which works the red/yellow/green LED.
 
Last edited:

upand_at_them

Joined May 15, 2010
896
Resistor codes don't start with zero. They are a version of “standard form”, a number between 1.00x10^n and 9.99x10^n, where n is the multiplier band.
How should 0.15 ohms be represented in 5-band code? Maybe the manufacturer (Chinese?) didn't follow standard form? I'm playing Devil's advocate.
 

sagor

Joined Mar 10, 2019
695
When the multiplier is very low, 0.01 (silver), it would be hard to designate a low value of resistance without a leading zero in a 5 band color code. Think about it, if you forced one to use at least brown or more for the first band, how do you show 0.01 ohms? There is no smaller multiplier than 0.01 (silver), is there?
 

BobTPH

Joined Jun 5, 2013
4,899
Yep, any value < 1 requires a leading zero in the 5 band code. I was surprised at that, but it appears to be true.

Bob
 

Ian0

Joined Aug 7, 2020
5,114
how do you show 0.01 ohms?
Colour-coded resistors that low in value are rare, because only leaded resistors have colour codes. When the resistance is that low, the resistance of the leads is starting to affect the overall value.
I'm also surprised to see a 5-band code, because <1Ω resistors tend to run in an E6 series.

Another thought - if you ignore the initial black band, then it becomes a perfectly valid 4-band code.
 

Thread Starter

AlbertHall

Joined Jun 4, 2014
12,020
because only leaded resistors have colour codes
It is a leaded resistor. It is open circuit and shows no sign of overheating or mechanical damage. The background colour is pale blue which made me wonder if it a fusible resistor.
 

Ya’akov

Joined Jan 27, 2019
5,659
It is a leaded resistor. It is open circuit and shows no sign of overheating or mechanical damage. The background colour is pale blue which made me wonder if it a fusible resistor.
It certainly could be but since the color code says 1% and blue is very common for 1% resistors, that seems to be the reason. On the other hand, if it is open, it lends some weight to your idea.
 

upand_at_them

Joined May 15, 2010
896
Got a photo? Could it be an inductor? Are there any obvious physical differences between an inductor and a resistor? The inductors I'm looking at on my bench right now have a pale blue background.
 

sagor

Joined Mar 10, 2019
695
Too bad the black wire hides the IC name.
I suspect it is a current shunt of some sort, and the rest of the circuit provides feedback as to overcurrent, etc.
There is nothing on that board that can handle any amount of "power", so it is strictly for monitoring I think.
 
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